Induction-motor.



s. R. BERGMAN.

INDUCTION MOTOR.

I ,1909. v 936,292. Patented Oct. 12, 1909.

Inventor Sven R. Ber man, b w" v H fittg. k

To all it my concern? Be itknown that I, SvnN -R. BERGiiiAN? a" suhjectnf the Kingof Sweden, residing at Lynn, county of Essex, State of Massachu setts; have invented certain new and use'fil'l' improvements Induction-Motors efwhih' the folliowinglis iais'pecificatihn. j

.My invention relates to induction motors, and its objectis to improve the startingchar tcteristics o f n otors having'secondary wind j section,'"of Zan induction'motor 1 ings of thesquirrel-ca e type; a

The squirne ,cag'e winding the simplest and cheapestforanof secondary winding for induction motors, but as compared with coil windings has hitherto possessed the dis'ad-l primary: Winding ing, since the reactanceofor varying the re'actance o vantage that resistance cannot be: inserted in circuit with it to reduce-the starting current" and to increase the sta torque 'By 'my invention this disadv'ah g ,is removed.-

A squirrelrcage winding 'i-n' a -well designed'induction niotorwith small air gap has comparatively low reactance, since the only, sortion of -the/winding which is era.- bedde .in ironzis'in" inductive relation to the and has .a'; comparatively small leakage flux. Y Y

My invention cohsis'tsin' roviding means f the end-rings of the squlrre cage winding. laccoinplish this by providing-1 a laminated magnetic'body,

which may be moved toward or away from the'eiidiing. At tartlng'the hody'is movedciosejtethei'endaring, which is thennearly embedded reactance is -high. When the mot-hr is up to speed'j the' magnetic body is moved away train the nd ring, so that the reactanceof the en dri'ng" is" reduced. to the usual small amount. Z

ing two end-rings in parallel at one end of the conductors ofthe squirrell-cage winding, one of these end-rings being of high resistance, and the other oit' low resistance. The" magnetic body is'movedtoward and away from the low re i tance end-ring- .Atstartf the lowresistance end-ringis high, becaiise. gi -the proximity of the ma etic mass, most of the current flows throng "the high resistance end-ring, so that. not only is the starting current reduced, but the starting torque. is relatively increased, as in an induction motor with a coil windin having a resistance inserted in, series w t the winding at starting. Whenthe motor is slia j-iiiniagneticrmaterial, so that its is low,

" a lowfi'esistance secondary winding.

1p to's cejd," the ma'gn tea e is' irnoved favvay' .ifTOIfi the -w resistance end er ing whichfthen carries ino'st ofythe current," so I j that the winding thenhas the flcharacteris-f Myfihwntion will besthe'nnrlerstoo ,hy"

reference tothe accompanying"drawing; inn-1 v: Figure 1 shows aside elevation, partly in ar rangec'llin" accordance with my invention; I Fig. 2 shows "an enlarged detail viewlof thelarninated'bodyQ v In the dr: 'wing's',"Aireptese t's-the'. station-$.70 4 ary primary winding;"a11d' B*the secondaryy 4 i x r otar'y windin'gg which not the-ysquirrel-- cage type. fAt the left-hand of the conduc, v. tors are placedtwo" end -rings' band b y which v are in parallel, end oneof which, b, has. a; 7-5 'low resistance, while the other, 6 is of small cross section, and, therefore, has a. high resistance. I i

C and C representtwo laminated niagneti 'masses which are carried by'the rotor These masses are in the form of ":disks; The disk Ci is fast to the rotor I shaft.- 'The'disk C while keyed to the rotor shaft'so as to rotate with it, is movable axially on the shaft. The sleeve 0, on which this magnetic disk is carried is engaged by a lever d pivoted on the motor" frame and provided with a handle D.

At starting the handle and disk 0 are in the position shown in Fig. 1. The low 0 resistance end-ring b is then nearly embedded inmagnetic material, so that the-reluctance for-the flux surrounding the end-ring and the reactance-of the end-ring, =therefore,"high, so that the greater part of 5 the current flows through the high resistance end-ring b and the starting characteristics of the motor are those of a motor having a high resistance'secondary. When the motor is up'to speedthe handle D is moved so as to shift the disk C to the left; awa from the end-ring-b. The reluctance of the flux path around the end-ring is thereby greatl ncreased, so that the reactance of the en ring is Inucli increased. The greater part of the secondarycurrent then flows through the. low resistance ring 6, and the motor 0 crates ,With 'the characteristics of a motor avingj In order to provide a solid cqlnpact conl10 winding, rel-cage type,

:. ringand thelaminae composing it 1n .varying the reactance of said preferably 'arrange struction of the disk C, I

the form of involutes, as shown in F1 2 Ldo not desire to l imit myself to the. par ticular construction and arrangement of parts here shown,-but aim in the appended claims to cover all modifications which are within the scope .of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is,.

1. An, induction motor havinga primary a secondary winding of the squirand' a starting evice comprisin means for varying the reactance of an en ring of the secondary windin 2.. An induction motor having a 's tation-v ary primary winding, a secondary rotor winding of thesquirrel-cage type, a laminated magnetic body-carried by the rotor, and means 7 for moving said body toward and away from an end ringof the secondary winding. v 3. An induction motor having a'primary winding, a secondary winding otthe squirrel-cage type having a high resistance enda low resistance end-ring in'parallel at one end of the secondary conductors, and a starting device comprising means for low resistance end-ring.v f;

4:. An induction motor having a stationary primary winding, ofthe squirr l-cage type havlng a high relaminae arranged in the form sistance end-ring and ailow-resistance end- .ring in parallel at one end of the secondary conductors, a'laminated magnetic body car-' ried by the rotor, and means for -moving saidbody toward resistance end-ring.

5; An induction motor having a stationary primary winding, a secondary rotor winding of the squirrel-cage type, a disk composed of magnetic laminae arranged in the form of involutes,'a.nd means formoving said disk toward and away from an end-ring of said secondary windlng.

6. An inductionmotor'having a stationary a secondary rotor winding sistance end-rlng and a low resistance endring in parallel at one end of the secondary conductors, a disk composed of magnetic and means for moving said diskvtoward and away from said low resistance end-ring. 1

In witness whereof, I have hereunto set my hand this 19th day of March, 1909,

SVEN "R." BERGMAN, Witnesses:

DUGALD MoK. MoKILLor, CHARLES A. BARSARD.

primary Winding, a secondary rotor winding of the squirrel-cagetype having a high reand away'from said low 

